[llvm] r257875 - [InstCombine] Rewrite bswap/bitreverse handling completely.

Fri Jan 22 06:52:38 PST 2016

Hi,

Yes, r257886 needs to be merged also. This appeases the msan bots, and could explain your segfaults (although I didn’t see any segfaults myself! unless this is a stage2 build?)

James

commit d6a317790ea52ead225a65c1c23b4f9fcd61ee2a
Author: James Molloy <james.molloy at arm.com>
Date:   Fri Jan 15 10:36:01 2016 +0000

    [CodeGenPrepare] Try and appease sanitizers

    dupRetToEnableTailCallOpts(BB) can invalidate BB. It must run *after* we iterate across BB!

    git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@257886 91177308-0d34-0410-b5e6-96231b3b80d8

> On 22 Jan 2016, at 14:13, Dimitry Andric <dimitry at andric.com> wrote:
>
> Hi Hans,
>
> After this merge, the release_38 branch starts failing a bunch of tests for me, due to segfaults:
>
> Failing Tests (7):
>    LLVM :: CodeGen/AArch64/arm64-call-tailcalls.ll
>    LLVM :: CodeGen/AArch64/cmpxchg-idioms.ll
>    LLVM :: CodeGen/ARM/call-tc.ll
>    LLVM :: CodeGen/ARM/cmpxchg-idioms.ll
>    LLVM :: CodeGen/X86/2012-01-16-mfence-nosse-flags.ll
>    LLVM :: CodeGen/X86/switch.ll
>    LLVM :: CodeGen/X86/tailcall-returndup-void.ll
>
> For example, with the AArch64 cmpxchg-idioms.ll test, it gives:
>
> FAIL: LLVM :: CodeGen/AArch64/cmpxchg-idioms.ll (10056 of 24459)
> ******************** TEST 'LLVM :: CodeGen/AArch64/cmpxchg-idioms.ll' FAILED ********************
> Script:
> --
> /home/dim/obj/llvm-258266-rel38-freebsd11-i386-ninja-rel-1/./bin/llc -mtriple=aarch64-apple-ios7.0 -o - /share/dim/src/llvm/release_38/test/CodeGen/AArch64/cmpxchg-idioms.ll | /home/dim/obj/llvm-258266-rel38-freebsd11-i386-ninja-rel-1/./bin/FileCheck /share/dim/src/llvm/release_38/test/CodeGen/AArch64/cmpxchg-idioms.ll
> --
> Exit Code: 2
>
> Command Output (stderr):
> --
> FileCheck error: '-' is empty.
>
> --
>
> Running the above llc command separately shows the segfault:
>
> $ gdb --args /home/dim/obj/llvm-258266-rel38-freebsd11-i386-ninja-rel-1/./bin/llc -mtriple=aarch64-apple-ios7.0 -o - /share/dim/src/llvm/release_38/test/CodeGen/AArch64/cmpxchg-idioms.ll
> [...]
> Starting program: /home/dim/obj/llvm-258266-rel38-freebsd11-i386-ninja-rel-1/bin/llc -mtriple=aarch64-apple-ios7.0 -o - /share/dim/src/llvm/release_38/test/CodeGen/AArch64/cmpxchg-idioms.ll
>        .section        __TEXT,__text,regular,pure_instructions
>        .ios_version_min 7, 0
> [New Thread 2a012000 (LWP 100435)]
>
> Program received signal SIGSEGV, Segmentation fault.
> [Switching to Thread 2a012000 (LWP 100435)]
> 0x08a92885 in (anonymous namespace)::CodeGenPrepare::runOnFunction(llvm::Function&) ()
> (gdb) bt
> #0  0x08a92885 in (anonymous namespace)::CodeGenPrepare::runOnFunction(llvm::Function&) ()
> #1  0x08e50d4b in llvm::FPPassManager::runOnFunction(llvm::Function&) ()
> #2  0x08e50ff2 in llvm::FPPassManager::runOnModule(llvm::Module&) ()
> #3  0x08e51577 in llvm::legacy::PassManagerImpl::run(llvm::Module&) ()
> #4  0x08e51c08 in llvm::legacy::PassManager::run(llvm::Module&) ()
> #5  0x081a2dd3 in compileModule(char**, llvm::LLVMContext&) ()
> #6  0x0819fe9c in main ()
>
> James, maybe you have an idea what is going wrong here?
>
> -Dimitry
>
>> On 19 Jan 2016, at 21:53, Hans Wennborg via llvm-commits <llvm-commits at lists.llvm.org> wrote:
>>
>> Thanks! r258180.
>>
>> On Tue, Jan 19, 2016 at 9:42 AM, David Majnemer
>> <david.majnemer at gmail.com> wrote:
>>> Yes.
>>>
>>> On Tue, Jan 19, 2016 at 9:33 AM, Hans Wennborg <hans at chromium.org> wrote:
>>>>
>>>> This should have baked on the buildbots for a while now.
>>>>
>>>> David, OK to merge?
>>>>
>>>> On Fri, Jan 15, 2016 at 10:25 AM, James Molloy <James.Molloy at arm.com>
>>>> wrote:
>>>>> Hi Hans,
>>>>>
>>>>> Yes, as long as David is happy please merge this, along with the
>>>>> followup that fixes msan.
>>>>>
>>>>> I was waiting for it to soak through the stage2 bots before suggesting
>>>>> it myself.
>>>>>
>>>>> James
>>>>>
>>>>>
>>>>>
>>>>>> On 15 Jan 2016, at 17:59, Hans Wennborg <hans at chromium.org> wrote:
>>>>>>
>>>>>> It was suggested that this be merged to 3.8. David, I think you're the
>>>>>> code owner here; OK for merge?
>>>>>>
>>>>>> On Fri, Jan 15, 2016 at 1:20 AM, James Molloy via llvm-commits
>>>>>> <llvm-commits at lists.llvm.org> wrote:
>>>>>>> Author: jamesm
>>>>>>> Date: Fri Jan 15 03:20:19 2016
>>>>>>> New Revision: 257875
>>>>>>>
>>>>>>> URL: http://llvm.org/viewvc/llvm-project?rev=257875&view=rev
>>>>>>> Log:
>>>>>>> [InstCombine] Rewrite bswap/bitreverse handling completely.
>>>>>>>
>>>>>>> There are several requirements that ended up with this design;
>>>>>>> 1. Matching bitreversals is too heavyweight for InstCombine and
>>>>>>> doesn't really need to be done so early.
>>>>>>> 2. Bitreversals and byteswaps are very related in their matching
>>>>>>> logic.
>>>>>>> 3. We want to implement support for matching more advanced
>>>>>>> bswap/bitreverse patterns like partial bswaps/bitreverses.
>>>>>>> 4. Bswaps are best matched early in InstCombine.
>>>>>>>
>>>>>>> The result of these is that a new utility function is created in
>>>>>>> Transforms/Utils/Local.h that can be configured to search for bswaps,
>>>>>>> bitreverses or both. InstCombine uses it to find only bswaps, CGP uses it to
>>>>>>> find only bitreversals.
>>>>>>>
>>>>>>> We can then extend the matching logic in one place only.
>>>>>>
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